Railway-tie pad



G. A. WILSON 2,770,421

RAILWAY-.TIE PAD Filed' May 19,4 1954 RAILWAY-TIE PAD George A. Wilson, Weston, Mass., assignor to Fabreeka Products Company, Boston, Mass., a corporation of Massachusetts Application May 19, 1954, Serial No. 430,831

6 Claims. (Cl. 23S-283) This invention relates to tie pads such as are used beneath the tie plates of a railroad to protect the ties from undue wear and deterioration. The employment of such pads beneath the tie plates reduces the cutting of the ties by the plates and extends the life of the tie, thus reducing the labor costs incident to tie renewal, and, because the gauge of the track is better maintained, saves labor costs for re-gauging, while the resiliency of the pad cushions the track structure from impacts, assures tight spikes and reduces the necessary size of tie plate.

Customarily such pads have been made of some resilient material for example, a felt-like substance consisting of fibrous material impregnated with or embedded in vulcanized rubber. It has recently been proposed to provide such pads with a moistureresistant layer at the underside of the pad between the pad and the tie, such moisture impervious layer acting as a seal to prevent the entry of water between the pad and tie or down into the tie following the spike. it has been found desirable to use a moisture impervious material which also forms an adhesive bond between the pad and the tie. There has also been a proposal to provide :a similar coating of adhesive moisture impervious material at the upper surface of the tie pad, but this has been objected to inasmuch as the tie plate is subject to movement under traffic, and thus should not be bonded to the pad and thus to the tie, leaving the plate to move independently of the tie, and at the'same time avoiding any tendency to break the adhesive seal between the bottom of the pad and the tie. A customary moisture impervious and adhesive material employed for this bottom layer of the pad is ordinary Trinidad asphalt.

Since these tie pads are of articles of ia type which makes it almost imperative that they be stacked one on another during shipment or storage, the presence of this layer or coating of asphalt, which at ordinary summer temperatures becomes quite sticky, makes it substantially impossible to stack the usual pads directly one on the other as is desirable, because they become so firmly adhered to each other that they cannot afterward be separated. Various proposals have heretofore been made to prevent such adhesion, one practice which has been used rather widely being to coat the exposed surface of the asphalt layer with powdered mica which so modifies the asphalt that the pads may be stacked one on the other without too much danger of adhering. However, since the intended effect of this mica coating is at least temporarily to diminish the :a-dhesiveness of the asphalt, the employment of the mica coating, to that extent at least defeats one of the intended purposes of the asphalt coating, that is to say, the firm adhesion of the pad to the tie. It is true that under the extremely heavy loads to which the pad is subjected during use and under some conditions of temperature, particularly summer temperature, the mica treated asphalt coating does retain a certain degree of adhesiveness sutcient to stick the pad to the tie. Such residual adhesiveness is not nearly so Patent ice great as that of the untreated asphalt, and thus the adhesion of the pad to the tie is not as firm nor as permanent as might be desired.

The present invention has for its principal object the provision of a railway tie pad, comprising the customarily relatively thick cushioning or body layer, :a relatively thin water-impervious adhesive layer, for example of asphalt, beneath the body layer, and means operative to prevent adhesion of stacked pads which does not appreciably detract from the normal adhesiveness of unmodified asphalt. Other and fuither objects and advantages of the invention will be pointed out in the following more detailed description and by reference to the accompanying drawings, wherein Fig. l is a fragmentary perspective View showing a portion of a railway track and indicating the location of the tie pad relatively to the tie plate and rail;

Fig. 2 is a fragmentary Vertical section illustrating one embodiment of the invention;

Fig. 3 is a fragmentary vertical section showing three tie pads, such as illustrated in Fig. 2, stacked one on the other;

Fig. 4 is a fragmentary vertical section through a tie pad also embodying the present invention, but showing the cushioning or body part of the pad as united to the tie-contacting layer by a thin layer of rubber cement, in accordance with a customary practice;

Fig. 5 is a View similar to Fig. 4, but illustrative of a slightly different embodiment, and

Fig. 6 is another view similar to Fig. 2, but illustrative of a pad having a body layer designed to provide a reservoir for the adhesive material such as forms the tie contacting layer.

In the attainment of the above objects, the present invention contemplates the provision of a thin protective film or layer applied to the upper surface of the cushioning layer or body portion of the pad, said thin upper film or layer which in use contacts the underside of the tie plate, being of a material which is abhesive as respects the material which forms the sticky tie contacting layer. The term abhesive has herein been adapted from the chemical industry as indicating the physical characteristic of refusing to adhere to other substances which are sticky or adhesive. While various materials do to a certain extent provide the desired abhesive characteristics, for example paraiiin or certain other waxes, the material which has been found to be most effective is silicone. The particular material which has been found most suitable and available is a colorless silicone product having the following physical characteristics Silicone content, percent i0() Color Coloriess to light straw This material has been found to impart abhesive and water-repellant characteristics to such materials as paper, glass, metal and stone and to minimize adhesion of such sticky materials as unvulcanized rubber, tar and asphalt. This material is liquid in the uncured state, dry and nonoily when cured, and is virtually odorless and colorless and inert to such materials as metals, glass, organic plastics and paper. It is soluble in a wide selection of solvents but insoluble in water. It boils in three to five minutes in 300 F. and in shorter periods in the presence of a suitable catalyst. It may be diiuted with aliphatic or aromatic hydracarbons, chlorinated solvents, acetone or methyl-ethyl ketone.

Referring to the drawings, there is shown in Fig. l a

length of railway rail R resting upon a tie plate P supported by the tie T and secured to the latter by a spike whose head is shown at S. lntervening between the plate P and the tie is the tie pad which forms' the subject matter of the present invention. As illustrated in Fig. 2', the tie pad 10 is shown as comprising a relatively thick body portion or' cushioning layer 11 which may be of any of the usual materials employed for the purpose, but which is preferably a vulcanized rubber compound con'- taining inclusions ofliber. Material suitable for the purpose is found in the scrap from the tire or belting industries, such material comprising cotton or other threads or bers comingled with rubber. It has heretofore been quite customary to make this cushioning layer of the order of one-fourth of an inch in thickness. To the underside of this cushioning layer 11 there is adhesively bonded a relatively thinner layer 1.2 of asphalt, such as Trinidad asphalt, devoid of inclusionsv of other materials and which thus possesses its full initial adhesiveness at elevated temperatures. This asphalt layer 12 may be of the order of one-sixteenth of an inchy in thickness, for example.

ln accordance with the present invention, there is ap plied to the upper surface of the cushioning layer 11 a thin coating or layer 13 of abhesive material such for example, as the silicone preparation above described. Preferably this is applied diluted with a volatile solvent such as above referred to, because when it is so diluted it takes a shorter time for the coating to dry than though the silicone were applied as a water emulsion. However, the form in which the silicone is applied is not essential to the present invention, it being sufficient that in the cornpleted product there is such a dry layer, coating or lm of abhesive material on the upper surface of the cushioning layer. l

When pads of this character are stacked one on another, as indicated in Fig. 3, where three pads 10a, 10b and 10c are shown as forming such a stack, the pads are arranged so that the silicone abhesive layer 13 of one pad is in contact with the exposed surface of the asphalt coating 12 of the next adjacent pad. Due to the peculiar characteristics of the lm or layer 13, there is but slight tendency of the asphalt layer to adhere to the pad adjacent to it, even though the pads be stacked to a substantial height, and even though exposed to atmospheric temperatures as high as any which may be encountered in railway practice.

Fig. 4 shows a pad slightly modified as respects that of Fig. 2, in that there is interposed between the asphalt layer and the cushioning layer a thin layer or coating 14 of rubber cement. Such an arrangement has been found desirable under certain circumstances, as providing a better bond between the pure asphalt and the cushioning layer wherein the rubber is vulcanized prior to the attachment of the asphalt.

1t has been found under certain circumstances that cushioning layers as thick as that above indicated are not essential, but since this material is available in the 1A inch layers, it has been proposed to provide the thinner cushioning layers by splitting one of the 1A inch layers so as to provide layers 1/8 inch thick. The splitting operation results in leaving a rough surface where some of the constituent fibers of the cushioning materiall project, as shown at 15 (Fig. 5), and these fibers provide a suflicient anchorage `for the asphalt, whereas otherwise it might be necessary to employ such a rubber cement layer as is shown in Fig. 4.

lt has been observed, at times, that a thin layer of asphalt such as shown in Figs. 2, 4 and 5 gradually loses its adhesive qualities, due in part to the fact that it is absorbed into the wood of the tie or seeps out edgewise, so that the desired characteristics of the asphalt layer may eventually be lost. In accordance with the present invenfil.

tion, it is proposed to provide an available supply of asphalt to replenish the layer 12, for example, by providing cavities or by punching holes in the cushioning layer 11, and then, in applying the asphalt, causing portions of the asphalt to intrude into these cavities or holes, thus providing what may be termed reservoirs 12a of asphalt in the substance of the cushioning layer which may gradually flow down so as to replace the layer 12 as the latter is exhausted.

While certain desirable embodiments of the invention have herein been illustrated and described by way of example, it is to be understood that the invention is broadly inclusive of any and all modifications, whether of materials employed or dimensions yof parts, which fall within the terms of the appended claims.

l claim:

l. A railway tie pad comprising a body layer of vulcaniZed rubber having fibrous material embedded therein, a tie-contacting bottom layer bonded to the body layer, said tie-contacting layer being relatively thin as compared with the body layer, the tie-contacting layer being weather-impervious and sticky, within the upper limits at least of the normal range of climatic temperatures, and a top layer relatively thin' as compared with the tie-contacting layer and integral with the body layer, the outer surface of said top layer being abhesive.

2. A railway tie pad comprising an elastic cushionlayer, a tie-contacting layer immediately below the cushioning layer, and integral therewith, the tie-contacting layer being relatively thin as compared with the cushion'- ing layer andl being of asphalt having its normal adhesive characteristics substantially unimpaired and a top layer thinner than the asphalt layer integral with the cushioning layer and having its top exposed surface abhesive. n

3. A railway tie padV according to claim 2, wherein the abhesive surface consists of silicone.

4. A railway tie pad according to claim 2, wherein the cushioning layer comprises comingled fabric and vulcanizedV rubber and has cavities therein which contain intrusions of the asphalt which forms the tie-contacting layer.

5. A railway tie pad according to claim 2, wherein the asphalt layer is bonded to the tie-contacting layer by rubber cement.

6. A railway tie pad comprising a body portion of resilient cushioning material, a bottom, tie-contacting layer of water-impervious material, said water-impervious material having the adhesive characteristics of asphalt, said layer being relatively thin as compared with the body portion, and a top layer integrally joined to the body layer, said top layer comprising a material whose exposed surface is abhesive to the material which forms the tie-contacting layer.

References Cited in the le of this patent UNITED STATES PATENTS OTHER REFERENCES Modern Railroads7 Gctober 1950, page 67. this is on tile in 23 8-283.)

(Copy of 

